How do you know if the medication you're using is working? One of the issues is that medications have different times for them to start working. When you put on a medication for any reason you should have some insight as to how long you have to wait for it to kick in. Different medications for IBD have different times when we anticipate them to work. Some can work in as short as a few weeks, but some can actually take a couple of months before they start working as well as we hope they do. The most accurate way to find out if there is inflammation, is to look inside the bowel.